Hydraulic drifter

ABSTRACT

A hydraulically-actuated percussion drill having a hydraulic control valve arranged so that hole-cleaner air can be directed through an axial passage in the piston without interference from the hydraulic valve; the piston is annular so that its central bore acts as an air passage. Oil drainage grooves are provided at the piston-housing joints where high pressure oil might otherwise tend to escape into the air passage; air pressure is used to retard leakage of oil past the grooves. Preferably the piston is built to include a cushioner flange which moves into hydraulic snubber cavities to decelerate the piston. The hydraulic supply system is such that high pressure oil is continually washed through the snubber cavities to take away heat developed by the snubbing actions.

' Feucht [151 3,701,386 [451 Oct.3l, 1972 [54] HYDRAULIC DRIFTER [72] Inventor; Jacob E. Feucht, Sidney, Ohio [73] Assignee: Dresser Industries, Inc.

[22] Filed: Dec. 11, 1970 1211 Appl. No.: 97,164

[52] US. Cl. ..17s/7s, 173/80, 173/116, 173/12l,l73/134 [51] Int. CL; ..B25d 9/00, B25d 17/14 [58] Field of Search ..173/80, 78, 105, 116, 134,

[56] References Cited UNITED STATES PATENTS 3,213,615 10/1965 Bjornberg ..173/134 1,709,024 4/ 1929 Katterjohn 173/105 3,490,549 1/1970 Catterson ..173/134 1,693,203 11/1928 Katterjohn ..173/105 2,821,963 2/1958 Curtis .L ..173/l34 3,231,032 1/1966 Genberg et a1. ..173/134 3,547,206 12/1970 Phillips ..173/l34 Primary ExaminerJames A. Leppink Attorney-John E. McRae, Tennes l. Erstad and Robert G. Crooks [5 7] ABSTRACT A hydraulically-actuated percussion drill having a hydraulic control valve arranged so that hole-cleaner air can be directed through an axial passage in the piston without interference from the hydraulic valve; the piston is annular so that its central bore acts as an air passage. Oil drainage grooves are provided at the piston-housing joints where high pressure oil might otherwise tend to escape into the air passage; air pressure is used to retard leakage of oil past the grooves. Preferably the piston is built to include a cushioner flange which moves into hydraulic snubber cavities to decelerate the piston. The hydraulic supply system is such that high pressure oil is continually washed through the snubber cavities to take away heat developed by the snubbing actions.

8 Claims, 2 Drawing Figures PKTENTEDBBIN I 72 SHEEI 20F 2 INVENTOR.

HYDRAULIC DRIFTER THE DRAWINGS FIG. 1 is a longitudinal sectional view taken through a percussion drill incorporating the invention.

FIG. 2 is a fragmentary sectional view taken on line I 2-2 of FIG. 2.

FIG. 1 IN GREATER DETAIL FIG. 1 shows a percussion drill having a two piece drill housing which slidably confines a striker piston 12 for movement toward and away from a drill steel 14.

patent). Piston 12 is suitably mounted within housing 10 for reciprocating motion as denoted by arrow 16; the piston has no rotational movement. Housing 10 is shown as two block-like housing elements 11 and 13 suitably secured together, as by through bolts (not shown).

Housing 10 contains an annular insert element 18 which separates the housing into two annular hydraulic chambers 22 and 24. In operation, chamber 22 is continually supplied with high pressure hydraulic fluid (oil), while chamber 24 is intermittently supplied with hydraulic fluid. Chamber 24 is a high work area chamber, while chamber 22 is a low work area chamber so that when chamber 24 is pressurized there is a leftward movement of piston 12 against drill steel 14; when chamber 24 is depressurized there is a reverse rightward movement of piston 12 away from the drill steel. Such cyclic or reciprocatory movement of the piston is preferably at high velocity, for example twelve hundred to fifteen hundred cycles per minute.

Piston 12 has its right end portion slidably disposedbetween theinner surface of fixed insert 18 and the outer surface of a two piece tubular air duct 28 which is secured in place by a cap element 30; the aforementioned bolts (not shown) mount the cap element on housing 10 so that the outer surface of duct 28 constitutes an inner surface of hydraulic chamber 24. The annular piston end area 26 exposed to chamber 24 constitutes the effective work area of chamber 24.

The extreme left end portion 32 of piston 12' has a slightly smaller diameter than the main portion 34 of the piston such that hydraulic fluid in chamber 22 acts on the piston differential area (area of 34 minus area of 32) to bias the piston rightwardly when chamber 24 is depressurized. The differential piston area is the effective work area of chamber 22.

The various piston diameters are chosen so that chamber 24 has a relatively high effective work area, for example 1.7 square inches, while chamber 22 has a relatively low work area, for example 0.3 square inches. As previously noted, when both chambers 22 and 24 are pressurized the piston 12 is moved leftwardly against drill steel 14, whereas when only chamber 22 is pressurized the piston is moved rightwardly away from the drill steel. The piston is shown just beginning its rightward motion.

HYDRAULIC FLUID SUPPLY In the illustrated percussion drill hydraulic fluid for pressurizing chamber 22 is supplied through a longitudinal passage 36 (FIG. 2) drilled into valve housing members 11, 13 and 30. The entrance end of passage 36 is at the right face of element 30, and is suitably threaded for connection of conventional hydraulic hoses (not shown) leading from a remote pump or other hydraulic source.

After the fluid has passed through chamber 22 it flows through a second drilled passage 49 to a cylindrical chamber 50 containing an accumulator piston 51; the space to the right of piston 51 is gas-charged to provide accumulator pressure for maintaining hydraulic chamber 50 at a suitable value, for example 1,200 psi. Hydraulic fluid intermittently flows from chamber 50 across a shuttle valve 44 into the aforementioned chamber 24 (FIG. 1). Valve 44 is so designed that in its non-illustrated position it permits fluid to flow from chamber 50 into chamber 24; in its FIG. 2 illustrated position the valve permits fluid to be exhausted from chamber 24 to a drain opening 42. Drain pressure is usually in the neighborhood of 30 p.s.i.

HYDRAULIC VALVE OPERATION To intermittently or cyclically pressurize and depressurize work chamber 24 it is necessary to alternately connect said chamber to high pressure space 50 and low pressure drain line 42. In the illustrated percussion drill this operation is accomplished by a shuttle valve 44 which is slidably positioned in a valve body 46 suitably mounted in housing element 13. Valve 44 includes a relatively small diameter pilot piston 48 whose upper end face is continually exposed to high pressure hydraulic fluid from space 50. Valve 44 also includes a larger diameter pilot piston 52 whose end face is intermittently exposed to high pressure hydraulic fluid in drilled chamber 54.

As shown in FIG. 2, line 54 is depressurized so that fluid pressure on the upper end face of piston 48 is effective to move valve 44 down to its illustrated position wherein valve groove 56 spans chamber 24 and exhaust groove 65; in this position chamber 24 exhausts to the drain opening 42.

When both chambers 50 and 54 are pressurized the differential piston area (area of piston 52 minus area of piston 48) cause valve 44 to be moved upwardly to a non-illustrated position wherein annular groove 56 spans chamber 24 and annular groove 58. In such a position the valve conducts high pressure fluid from space 50 into chamber 24.

In general, the position of valve 44 is controlled by the state of pressurization or depressurization of chamber 54; in the usual case such pressurizationdepressurization actions will be cyclic at rates of several hundred cycles per minute, timed by piston I2. The function of valve 44 is to cyclically connect chamber 24 with alternate ones of grooves 58 and 65 so that chamber 24 may be cyclically pressurized and depressurized.

PRESSURIZATION OF CHAMBER 54 Pressurization of chamber 54 is initially achieved by trapping high pressure fluid in the fluid passage system comprising slots 78, drilled holes 80, 81 and 82 machined groove 74, and chamber 54. High pressure fluid is initially supplied to groove 78 while piston 12 is in a rightward position wherein its annular groove 84 spans annular housing groove 75 and housing slots 78. The illustrated device uses two diametrically spaced slots 78 which connect with two drilled holes 80 and a surrounding annular groove 83. FIGS. 1 and 2 are taken at right angles to one another so that one of the slots 78 is shown in cross section in FIG. 2 and in dotted plan in FIG. 1. FIG. 2 is on a larger scale than FIG. 1 to show greater detail.

When piston 12 is displaced rightwardly from its illustrated position groove 84 interconnects slots 78 with annular groove 75. High pressure fluid can thereby fill the passage system comprising passage 36, hole 66, annular groove 68, hole 67, annular groove 75, groove 84, slots 78, holes 80, 81 and 82, groove 74 and chamber 54. This action pressurizes chamber 54.

During leftward movement of piston 12 chamber 54 remains pressurized until groove 84 registers with two diammetrically spaced slots 85 formed in the inner face of insert 18. At this time groove 84 spans slots 78 and 85 to form a path for depressurizing chamber 54. Depressurization involves reverse flow from chamber 54 through groove 74, holes 82, 81, and 80, slots 78, groove 84, slots 85, drilled holes 87 and 88, and auxiliary drain passage 89. Passage 89 may connect with main drain port 42, although such a connection is not shown.

In its illustrated position piston 12 has moved to the leftward limit of its motion and is just starting back on its rightward stroke. Groove 84 bridges across housing slots 78 and 85 so that chamber 54 is depressurized. Valve 44 is therefore in its illustrated position wherein chamber 24 is vented to drain 42. Chamber 22 is pressurized, but chamber 24 is not; therefore piston 12 is biased in a rightward direction.

As piston 12 moves rightward to a position wherein groove 84 bridges across slot 78 and groove 75 the control chamber 54 becomes pressurized to move valve 44 upwardly to open port 58 and close port 65. High pressure fluid thereby flows from space 50 through port 58 into chamber 24 to pressurize that chamber and cause a reverse leftward movement of piston 12.

PISTON SNUBBER ACTION Above mentioned US. Pat. No. 3,490,549 shows a striker piston having an enlarged head or flange 134 that moves through a semi-confined'mass of hydraulic fluid to cushion or snub the piston movement as the piston nears the limits of its travel, thereby minimizing cavitation effects and reducing shocks, as during overtravel when the drill steel is operating in air or against low resistances resulting from loose soil formations. In the present apparatus piston 12 is provided with a cushioner flange 91 whose diameter is slightly less than the diameters of the annular cavities 90 and 92 located at opposite ends of chamber 22. The central space area 94 of chamber 22 has a much larger diameter than flange 91 so that the flange can move relatively freely through the body of liquid until it reaches cavity 90 or 92. As the piston flange moves into either one of cavities 90 and 92 a mass of liquid is trapped within the respective cavity. The trapped liquid can escape from the cavity only by flowing past the outer edge surface of flange 91; the small clearance between the flange diameter and the cavity diameter produces a flowthrottling action that impedes the escape of the liquid, thereby slowing the piston before it actually strikes the blind end wall surface of the cavity. The snubbing action is achieved at each limit of piston movement; cavity acts to decelerate the piston during its rightward movement and cavity 92 acts to decelerate the piston during its leftward movement.

The snubbing action of cavities 90 and 92 is accompanied by the production of a certain amount of heat in the trapped oil. It is therefore preferred to have a positive continual flow of oil through chamber 22 so that new oil is admitted to the chamber for every successive cycle, such that heat of snubbing is carried away with the spent liquid. In the illustrated construction work chambers 22 and 24 are in series flow relation so that the fluid must flow through chamber 22 and then through chamber 24 in a single path; chambers 22 and 24 are not in parallel flow paths. The arrangement is such that the chamber 22 displacement is entirely exhausted through the single hole 39, thus insuring a positive oil flow through chamber 22 and a positive carry off of the heat developed by the snubbing action of piston flange 91 in the snubbing chambers 90 and 92. Preferably supply hole 37 and exhaust hole 39 connect with opposite face areas-of chamber 22 to further insure against stagnation in the chamber.

HOLE CLEANING In some situations the drilling rate is improved by forcing air into the hollow drill steel which carries the drill rod and bit. The illustrated drill includes an annular piston 12 whose inner surfaces 96 form an air passage extending the length of the piston. The arrangement permits a compressed air hose (not shown) to be connected onto cap 30 so that compressed air can flow through tubular member 28 and thence through piston passage 96 to a registering passage 97 in drill steel 14.

Preferably the piston bore is itself used as the compressed air passage; i.e. there is no separate air tube extending through the piston. A piston-formed air passage can be more generously sized than can a separate air tube; consequently more air flow can be provided for a given supply pressure. Also, the striker piston can have some misalignment with respect to drill 4 steel 14 without loss of air flow. When a separate air tube is employed special seals and clearances must be provided to compensate for the inevitable misalignments or cocking actions that occur when the striker piston bangs down on the drill steel.

In the illustrated construction the air passage is sealed by a flap type seal 100 at the work output end of the drill, and by the fit of piston 12 on the air admission tube 28. The piston-is sufficiently guided at its two diameters 32 and 34 so that piston-housing misalignment is minimal at the right end of the piston.

Ordinarily drill steel 14 includes an attached hexagonal drill rod, not shown, on the order of 12 feet long. The entire drill is usually mounted on a feeder chain located in an elongated feed channel; as the drilling proceeds the drill and the drill steel advance as a unit along the feed channel in the direction of the hole being drilled. The drill rod is guided by a bushing at the forward end of the feed channel so that at the beginning of the feed operation the drill steel is adequately guided at two widely spacedpoints (the drill and the bushing). However, as the feed operation proceeds the two guide points come closer together, so that any misalignments or transverse vibrations of the guide structures tend to stress or bind the drill steel. It

striker piston and drill steel rather than through a separate air tube the problems of tube-piston misalignments or tube-drill steel misalignments are avoided.

DRILL STEEL ROTATION Drill steel rotation can be achieved through any suitable drive means, but as shown in FIG. 1, the drive system comprises a fluid motor 102 having a splined drive shaft 104 keyed to a gear 106 which drives a second hollow gear 108. The second gear is rotatably mounted in radial sleeve bearings 110 and 112, and is passage 89. Groove 122 connects with drilled hole 130.

The system of grooves and passages serves to drain off high pressure liquid from chambers 22 and 24 before it can escape into the space defined by surfaces 96. The drain back system is enhanced because the pressure in passage 96 isusually higher than the hydraulic pressure, for example 100 p.s.i. air pressure vs. 30 psi. oil drain pressure. The air pressure, alone or in conjunction with O ring seals (not shown), promotes drainage of oil back to drain 89 rather than into the compressed air system where it would be non-recove rable.

The ability of the pressurized air to promote oil drainage is due to the fact that the inner surface 96 of the piston is used as the air passage; i.e. there is no separate air tube that would isolate the pressurized air from the piston-housing joints.

PISTON RETURN ASSIST The left end face area of piston 12 exposed to prespassage 89 via a surized air is somewhat greater than the right end face provided with a plurality of axial grooves 114, each of which contains two ball elements 116. Mating grooves 118 in an enlarged diameter portion of drill steel 14 trap the ball elements, whereby the elements constitute keys or drivers for transmitting gear 108 rotation into drill steel rotation while permitting axial displacement of the drill steel by the hammer action of striker piston 12. Ball elements 116 reduce friction effects between the gear and drill steel, while enabling the drill steel to have a desirable wobble or looseness relative to the housing.

Flap seal 100 is mounted in an annular cap plate 103 having a central hole 105 which defines a bearing for the reduced diameter shaft portion of the drill steel. The bearing is remote from the drive ball elements 116 so that the bearing doesnot hamper the aforementioned wobble action.

HYDRAULIC SEALS The hydraulic pump and reservoir for supplying passage 36 with hydraulic fluid is usually of limited capacity such that leakage of hydraulic fluid is undesirable. Unless piston 12 adequately seals the hydraulic system there is a possibility that hydraulic fluid can leak from high pressure work chambers 22 and 24 into the air passage 96 or out of the housing interior along the joint between housing 10 and drill steel 14. The illustrated drill is therefore equipped with two annular oil drainage grooves 120 and 122.

Groove 120 is fonned in the outer surface of tubular member 28 so that high pressure liquid in chamber 24 must pass into groove 120 before reaching the compressed air passage defined by surface 96. Groove 120 communicates with a drilled hole 124 and annular groove 126 formed by the two component tube elements 29 and 31 of air tube 28. Groove 126 in turn communicates with a drilled hole 128 leading to drain area exposed to pressurized air. Therefore. the pressurized air has a continual biasing action on the piston tending to move or return to the right. Because of this constant biasing air force it is possible to make the effective work area of chamber 22 slightly smaller than would otherwise be the case. The smaller hydraulic chamber area or displacement somewhat reduces the total hydraulic fluid requirements.

contemplated hydraulic pressures are relatively high so that various joints between the component parts must be sealed to properly confine the high pressure fluids to-the desired flow paths. Hence in practice 0- ring seals should be used between the striker piston and its fixed housing and between the shuttle valve and its housing. Additional seals should be provided between housing elements 11 and 13, and between valve body 46 and housing element 13.

I claim:

1. A percussion drill having a housing and a striker piston-drill steel assembly disposed therein; said housing defining separate hydraulic chambers alternately pressurized, one above the other, for reciprocating the piston back and forth in the housing; said drill steel having a reduced diameter shaft portion extending through a bearing at the work output end of the housing and an enlarged impact-receiver portion loosely keyed to a surrounding drive gear within the housing, whereby the drill steel can wobble about the bearin while being rotated by the drive gear.

2. The drill of claim 1 wherein the piston and drill steel are formed with communicating air passages for hole-cleaner air, and the housing is provided with an air seal at the bearing-drill steel joint such that compressed having annular hydraulic drain grooves at the pistonhousing joints where hydraulic liquid could otherwise leak from the pressurized work chamber to the piston air passage.

4. The drill of claim 3 and further comprising means for causing the air pressure to be materially higher than the hydraulic drain pressure, whereby the air pressure prevents leakage of hydraulic liquid from the associated drain groove into the piston air passage.

5. The drill of claim 3 wherein the piston air passage comprises a relatively small diameter hole-cleaner air passage extending rearwardly from the striker end of the piston, and a relatively large diameter counterbore extending forwardly from the rear end of the piston; said housing including a fixed air admission tube extending forwardly into the counterbore to deliver air to the small diameter passage.

6. The drill of claim 5 wherein the outside diameter of the piston at its striker end is larger than the diameter of the counterbore, whereby the air pressure continually exerts a rearward bias on the piston.

7. A percussion drill comprising a striker piston slidably confined within a drill housing; a first low area work chamber continually pressurized with hydraulic liquid for moving the piston in one direction, and a second high area work chamber intermittently pressurized with hydraulic liquid for moving the piston in the other direction; said piston having an enlarged cushioner flange arranged within the first continually pressurized chamber; said first chamber comprising a central chamber space materially larger in diameter than the cushioner flange, and reduced diameter end cavity spaces only slightly larger in diameter than the cushioner flange, whereby the piston can move freely while the flange is in the central chamber space but less freely when the flange enters either end cavity.

8. The drill of claim 7 wherein the entire hydraulic supply is initially admitted to the low area work chamber, thereafter to the high area work chamber, and finally to the drain. 

1. A percussion drill having a housing and a striker pistondrill steel assembly disposed therein; said housing defining separate hydraulic chambers alternately pressurized, one above the other, for reciprocating the piston back and forth in the housing; said drill steel having a reduced diameter shaft portion extending through a bearing at the work output end of the housing and an enlarged impact-receiver portion loosely keyed to a surrounding drive gear within the housing, whereby the drill steel caN wobble about the bearing while being rotated by the drive gear.
 2. The drill of claim 1 wherein the piston and drill steel are formed with communicating air passages for hole-cleaner air, and the housing is provided with an air seal at the bearing-drill steel joint such that compressed air is prevented from leaking through the work output end of the drill.
 3. A percussion drill comprising a striker piston slidably confined within a drill housing; a first low area work chamber continually pressurized with hydraulic liquid for retracting the piston, and a second high area work chamber intermittently pressurized with hydraulic liquid for advancing the piston; said piston having a passage therethrough for conducting high pressure hole-cleaner air to the hole being drilled; said housing having annular hydraulic drain grooves at the piston-housing joints where hydraulic liquid could otherwise leak from the pressurized work chamber to the piston air passage.
 4. The drill of claim 3 and further comprising means for causing the air pressure to be materially higher than the hydraulic drain pressure, whereby the air pressure prevents leakage of hydraulic liquid from the associated drain groove into the piston air passage.
 5. The drill of claim 3 wherein the piston air passage comprises a relatively small diameter hole-cleaner air passage extending rearwardly from the striker end of the piston, and a relatively large diameter counterbore extending forwardly from the rear end of the piston; said housing including a fixed air admission tube extending forwardly into the counterbore to deliver air to the small diameter passage.
 6. The drill of claim 5 wherein the outside diameter of the piston at its striker end is larger than the diameter of the counterbore, whereby the air pressure continually exerts a rearward bias on the piston.
 7. A percussion drill comprising a striker piston slidably confined within a drill housing; a first low area work chamber continually pressurized with hydraulic liquid for moving the piston in one direction, and a second high area work chamber intermittently pressurized with hydraulic liquid for moving the piston in the other direction; said piston having an enlarged cushioner flange arranged within the first continually pressurized chamber; said first chamber comprising a central chamber space materially larger in diameter than the cushioner flange, and reduced diameter end cavity spaces only slightly larger in diameter than the cushioner flange, whereby the piston can move freely while the flange is in the central chamber space but less freely when the flange enters either end cavity.
 8. The drill of claim 7 wherein the entire hydraulic supply is initially admitted to the low area work chamber, thereafter to the high area work chamber, and finally to the drain. 